class RuboCop::Cop::Performance::RedundantStringChars

def build_good_method(method, args)
  case method
  when :[], :slice
    "[#{build_call_args(args)}].chars"
  when :first
    if args.any?
      "[0...#{args.first.source}].chars"
    else
      '[0]'
    end
  when :last
    if args.any?
      "[-#{args.first.source}..-1].chars"
    else
      '[-1]'
    end
  when :take
    "[0...#{args.first.source}].chars"
  when :drop
    "[#{args.first.source}..-1].chars"
  else
    ".#{method}"
  end
end